A device for pressurizing a material to be pressed at a constant target load is well known, wherein the device has a mechanism that uses a servomotor and a load detector. The mechanism feeds the load detected by the detector back to the servomotor, and controls the load at a constant target load (e.g., Patent Documents 1 and 2).
However, the rod of the electric cylinder of the device moves at a velocity of 5 mm/s or more. Therefore, the rod does not stop at the target load for pressurizing because of the inertia of the device, etc., and a significantly bigger load may be applied to the material to be pressed than the target load. Thus, the device has problems in that the material cannot be appropriately pressured, also in that the load detector can be broken by being overloaded, etc.
Therefore, a method is typically used by the speed of the rod of electric cylinder being decreased to about 1 mm/s just before the rod bumps against the material (e.g., Patent Document 3).
However, in this method, the speed of the rod must be greatly decreased, and thus the time needed for pressurization will be extremely long. Especially, if this method is used for a process in which the pressurizing must be repeated in a short cycle, there will be a problem in that its productivity will be inevitably decreased.
Further, a method for pressurizing is proposed to resolve the problem. In that method, after the end of the rod of the electric cylinder bumps against the material and before the load for pressurizing reaches a target load for pressurizing, the speed of the rod will be decreased at a constant rate, or at a proportional rate (e.g., Patent Documents 4 and 5).    Patent Document 1: Japanese Patent Publication Laid-open No. 2005-138110    Patent Document 2: Japanese Patent Publication Laid-open No. 2009-101419    Patent Document 3: Japanese Patent Publication Laid-open No. H11-193598    Patent Document 4: Japanese Patent Publication Laid-open No. H09-314399    Patent Document 5: Japanese Patent Publication Laid-open No. 2005-254290